JPH0354786B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an oxygen meter used in an oxygen deficiency meter, an oxygen enrichment device, an anesthesia device, etc. More specifically, the present invention relates to an oxygen meter used in an oxygen deficiency meter, oxygen enrichment device, anesthesia device, etc. , relates to an oxygen meter that can automatically predict or detect the life of an oxygen meter cell.

<Prior Art> For example, a galvanic cell type oxygen meter is used in the oxygen deficiency meter, oxygen enrichment device, anesthesia device, etc.
This oxygen meter detects the oxygen concentration in the sample gas from the reduction plateau current that occurs when oxygen diffused and absorbed into the electrolytic cell through a gas-permeable diaphragm is reduced on the electrode surface.It is small and lightweight. , which itself generates an electrical signal, is widely used in the devices mentioned above.

Such oximeters are rarely used continuously and are usually used in batches. Before use, it must be calibrated in air. In other words, since there is a known amount of oxygen (approximately 21%) in the air,
Calibrate the oxygen meter using this as a reference gas. This calibration operation is necessary to maintain measurement accuracy, but
The operation was troublesome because it had to be done manually, and sometimes the calibration operation was forgotten.

Furthermore, in conventional devices, it is extremely difficult for a general oxygen meter user to predict the life span of the oxygen meter cell.

<Problems to be Solved by the Invention> The first technical problem to be solved by the present invention is to eliminate the need for manual calibration in the oxygen meter, and to automatically perform calibration when using the oxygen meter. A second technical problem to be solved by the present invention is to predict or detect the lifespan of the oximeter cell and to automatically display this.

<Means for Solving the Problems> A first aspect of the present invention includes an adder having an input supplied with a detection signal from an oximeter cell, and one input having a reference voltage corresponding to a known amount of oxygen. A comparator with the output voltage of the adder applied to the other input, and a comparator that is reset when the device power is turned on, and after the reset is released, counts the clock given from the oscillation circuit described later, and this circuit a counter that latches the value at that time when the oximeter stops oscillating, an oscillation circuit that starts and stops oscillation according to a predetermined output level of the comparator, and a voltage related to the detection signal from the oximeter cell. The D/A converter is applied to a power supply terminal, converts the output of the counter into digital/analog, and applies the converted signal to the adder as an addition input, and means for displaying the output signal of the adder. There is.

In addition to the configuration of the first invention, the configuration of the second invention of the present invention is such that, in addition to the configuration of the first invention, the output of the counter is provided,
A check circuit is provided which generates an alarm signal when the count value exceeds a predetermined value.

<Operation> The first invention operates as follows. That is,
The oxygen meter cell is placed in an atmosphere containing a known amount of oxygen, and each time the device is turned on, an electrical calibration operation is performed to match the output voltage of the adder with the reference voltage of the comparator. The specified coefficient is held, and thereafter, this coefficient is used to generate an output signal proportional to the detection signal until the next calibration.

The second invention operates as follows. That is,
In addition to the effects of the first invention, the output signal of the check circuit is applied to the display means to display the life span of the oximeter cell.

<Examples> Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an apparatus according to an embodiment of the present invention. In the figure, 1 is an oxygen meter cell such as a galvanic cell type oxygen meter, and 2 is the output voltage from the oxygen meter cell 1.
A preamplifier 3 for amplifying Vi is an adder, and the output voltage Vo of the amplifier 2 is applied to the non-inverting input terminal.

Part A surrounded by a dashed-dotted line is a calibration circuit part that automatically adjusts the coefficient of the output voltage. Among these parts, one input is given a reference voltage Vs corresponding to, for example, the amount of oxygen in the air, and the other input is is a comparator to which the output voltage VO' of adder 3 is applied; 5 is a flip-flop which is set and reset according to the state of the output of this comparator; 6 is an oscillation circuit;
Oscillation is started and stopped based on the output of the flop 5. 7 is a counter that counts clock pulses given from the oscillation circuit 6 and latches the value at that time when the oscillation of the oscillation circuit 6 stops; 8 is a reset circuit that generates a reset pulse at the same time as the device is powered on; the output pulse is It is applied to the reset terminals of flip-flop 5 and counter 7. 9 is a D/A converter to which the output voltage Vo of the amplifier 2 is applied to the power supply terminal, converts the output of the counter 7 from digital to analog, and outputs Vb to the adder 3.
is applied to the inverting input terminal of .

10 is an A/D converter that converts the output voltage Vo' of the adder 3 into a digital signal, and 11 is a display unit that digitally displays the contents of the output of the A/D converter 10.

Reference numeral 12 designates a check circuit which receives the output of the counter 7 and generates an alarm signal regarding the lifespan of the oximeter cell 1 when the count value exceeds a predetermined value.

FIG. 2 is a circuit diagram showing a specific configuration of the check circuit 12 and D/A converter 9 in the apparatus according to the embodiment of the invention shown in FIG. For example, an 8-bit binary counter is used as the counter 7, and a clock pulse from the oscillation circuit 6 is applied to the clock terminal CK. The D/A converter 9 includes an 8-bit D/A converter 9a whose power supply terminal Vref is supplied with the output voltage Vo of the amplifier 2 and whose input is supplied with the output from the counter 7. The inverting output of this converter is applied to the inverting input of the adder 3. The check circuit 12 includes an AND gate 12a to which the upper 4 bits of the counter 7 are applied, an AND gate 12b to which the lower 4 bits of this counter are applied, and an AND gate 12 to which the outputs of these gate circuits are applied.
c.

The operation of the apparatus according to the embodiment of the present invention constructed as described above will be explained with reference to the timing chart shown in FIG. In Figure 3, diagram a is the device power supply voltage, diagram b is
is the output voltage Vo' of the adder 3, Figure c is the reset pulse from the reset circuit 8, Figure d is the output voltage of the comparator 4, Figure e is the output of the flip-flop, and Figure f is the clock pulse given from the oscillation circuit 6. , figure g
represent the output Vb of the D/A converter 9, respectively.

Place the oxygen meter cell 1 in an air atmosphere and turn on the device power. At the same time as the device power is turned on, a reset pulse is generated from the reset circuit (FIG. c), and the flip-flop 5 and counter 7 are thereby reset.

As a result, the output Vb of the D/A converter 9 becomes zero, and the output Vo' of the adder 3 becomes the output of the amplifier 2.
Vo is output as is (Vo′=Vo).

In comparator 4, adder 3
While the output Vo' is in the relationship Vo'<Vs, the output is at H level (Fig. d).

In this state, when the reset is released,
Due to the output of the flip-flop 5 (FIG. e), the oscillation circuit 6 starts oscillating (FIG. f), and the counter 7 starts counting up.

The output of the counter 7 is converted into a voltage signal Vb by the D/A converter 9, and added to Vo in the adder 3 (Figure a). The output of the adder 3 is expressed as Vo'=Vo+Vb (1), and when this value becomes larger than the reference value Vs, the output of the comparator 4 is inverted and the oscillation of the oscillation circuit 6 is stopped. When the oscillation of the oscillation circuit 6 stops, the counter 7 latches the current value, thereby completing the calibration operation.

That is, in the D/A converter 9a, the full scale is counted by N, and the output of the latched counter 7 is counted by M.
In the case of a count, the output Vo is weighted by α=M/N to generate the output α·Vo. This output is further inverted by an inverter 9b and applied to the inverting input terminal of the adder 3 as an output Vb=-α·Vo.

As a result, the adder 3 performs the calculation Vo'=(1+α)・Vo...(2), and from then on, when the oxygen meter cell 1 is placed in the sample gas, the detection signal Vo is added to the coefficient (1+α).
generates a (calibrated) output Vo′ multiplied by α). This signal voltage is applied to the display unit 11 via the A/D converter 10 and displayed as the oxygen concentration of the sample gas.

Such a calibration operation is performed every time the device is powered on, α is changed according to the state of the oxygen meter cell 1, and calibration at the air point is automatically performed.

On the other hand, in the check circuit 12, for example, when the upper 4 bits of the output of the counter 7 are at H level, it is determined that the state is just before the calibration limit, and gives an output representing this state, that is, the output of the gate 12a, to the display section 11, and also , when all bits become H level, this is determined to be the calibration limit, and the output of the gate 12c representing this state is given to the display unit 11, and the calibration limit notice (lifetime notice of the oxygen meter cell 1) and the calibration limit ( The lifespan of the oxygen meter cell 1) is displayed.

<Effects of the Invention> According to the present invention, an oximeter can be calibrated automatically, and the life of an oximeter cell can be automatically predicted or detected.

In the explanation of the embodiments of the present invention so far, air is used as the reference gas, but the comparison is not limited to this, even if oxygen gas with a concentration of 100% or a gas with a known amount of oxygen is used. Calibration can be similarly performed by changing the reference voltage Vs of the device 4 in accordance with the oxygen concentration of the reference gas.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an apparatus according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a specific configuration of a portion of the apparatus according to an embodiment of the invention shown in FIG. 1, and FIG. 3 is an embodiment of the invention shown in FIG. 1. This is a timing chart to explain the operation of the device. 1... Oxygen meter cell, 3... Adder, 4... Comparator, 6... Oscillation circuit, 7... Counter, 9...
D/A converter, 11...display section, 12...check circuit.

Claims (1)

[Claims] 1. An adder to which the detection signal from the oximeter cell is applied to one input, a reference voltage corresponding to a known amount of oxygen is applied to one input, and the output of the adder to the other input. The comparator to which voltage is applied is reset when the device power is turned on, and after the reset is released, it counts the clock given from the oscillation circuit described later, and when this circuit stops oscillating, the value at that time is latched. an oscillation circuit that starts and stops oscillation according to a predetermined output level of the comparator; a voltage related to the detection signal from the oximeter cell is applied to a power terminal; A D/A converter converts it into analog and applies it as an addition input to the adder, and means for displaying the output signal of the adder, and the oximeter cell is placed in an atmosphere containing a known amount of oxygen. , each time the device is powered on, the output voltage of the adder is calibrated to match the reference voltage of the comparator, and thereafter an output signal is generated based on the coefficient held at this time. Oxygen meter. 2 Comparison of an adder whose input is given a detection signal from an oximeter cell, and a reference voltage corresponding to a known amount of oxygen is applied to one input, and the output voltage of the adder is applied to the other input. a counter that is reset when the device power is turned on, counts the clock given from the oscillation circuit described later after the reset is released, and latches the value at that time when this circuit stops oscillating; an oscillation circuit that starts and stops oscillation according to the output level of the device;
a D/A converter to which a voltage related to the detection signal from the oximeter cell is applied to a power supply terminal, converts the output of the counter into digital/analog, and applies the converted signal to the adder as an addition input; means for displaying an output signal; and a check circuit for generating an alarm signal when the output of the counter is applied and the count value exceeds a predetermined value, and the oxygen meter cell is placed in an atmosphere containing a known amount of oxygen. put,
Every time the device power is turned on, the output voltage of the adder is calibrated to match the reference voltage of the comparator, and thereafter an output signal is generated based on the coefficient held at this time, and the check circuit is calibrated. An oximeter characterized in that an output signal is given to the display means to display the life span of the oximeter cell.